Aug. 12, 2011 -- A rapid blood test that distinguishes between viral and bacterial infection in less than two hours could prove to be a useful weapon in the battle against antibiotic resistance.

Researchers in Israel say they have developed just such a test, but they add that more research is needed to confirm their findings.

The test relies on a process known as chemiluminescence, which measures light emitted in response to chemical reactions.

They found that white blood cells known as phagocytes produced to fight bacteria and viruses had different chemiluminescent signatures that could be easily seen in blood samples within just a few hours.

Viral and Bacterial Symptoms Can Be Similar

Bacteria and viruses are the most common cause of respiratory infections, such as pneumonia and bronchitis.

The different infections often have very similar symptoms, but antibiotics are only useful in the treatment of illness caused by bacteria.

Cultures are most commonly used in the general practice setting to distinguish between the two types of infection, but it typically takes 24 to 48 hours to confirm a diagnosis.

As a result, antibiotics are often prescribed unnecessarily to people who turn out to have viral infections. This practice has greatly contributed to the growing problem of antibiotic resistance.

In a new study, published this week in the journal Analytical Chemistry, researchers Robert Marks, PhD, and Daria Prilutsky, PhD, examined the ability of a chemiluminescence-based blood test they developed to distinguish between viral and bacterial infection in blood samples taken from 69 patients treated in the emergency department of a hospital in Israel.

All the patients had fevers and all had been diagnosed as having viral or bacterial infections.

The phagocyte-targeting model developed by the researchers was able to distinguish between viral and bacterial infection with a high predictive accuracy.

Marks say the goal is to be able to also identify fungal and parasitic infection in future generations of the experimental blood test.

Antibiotic Resistance a ‘Public Health Crisis’

Marks tells WebMD that the next step is to confirm the current findings in a larger group of patients and develop software to make applicable to the clinical setting.

Prilutsky adds that the goal is to develop a cost-effective, rapid blood test for clinical use within two or three years.

"We are at the beginning, but we believe this test could help reduce the overuse of antibiotics by quickly identifying viral and bacterial infection,” she tells WebMD.

Ginocchio is chief of the division of infectious disease diagnostics at the North Shore-LIJ Health System in Lake Success, N.Y.

She tells WebMD that pharmaceutical companies are not developing new drugs to replace older antibiotics because there is no economic incentive to do so.

Quickly identifying which infections will and will not respond to antibiotics will be increasingly important as older drugs stop working, she says.

“We already have organisms that are resistant to every drug we throw at them,” she tells WebMD. “We have to take a hard look at what we are doing and if we don’t change clinical practice we may not have many useful antibiotics left to treat with within a decade.”